Micromechanical detection structure for a MEMS sensor device, in particular a MEMS gyroscope, with improved driving features

ABSTRACT

A micromechanical detection structure includes a substrate of semiconductor material and a driving-mass arrangement is coupled to a set of driving electrodes and driven in a driving movement following upon biasing of the set of driving electrodes. A first anchorage unit is coupled to the driving-mass arrangement for elastically coupling the driving-mass arrangement to the substrate at first anchorages. A driven-mass arrangement is elastically coupled to the driving-mass arrangement by a coupling unit and designed to be driven by the driving movement. A second anchorage unit is coupled to the driven-mass arrangement for elastically coupling the driven-mass arrangement to the substrate at second anchorages. Following upon the driving movement, the resultant of the forces and of the torques exerted on the substrate at the first and second anchorages is substantially zero.

BACKGROUND Technical Field

The present disclosure relates to a micromechanical detection structurefor a MEMS (Micro-Electro-Mechanical System) sensor device with improveddriving features. In particular, the following discussion will makereference, without this implying any loss of generality, to use of themicromechanical detection structure in a MEMS gyroscope.

Description of the Related Art

As is known, micromachining techniques enable manufacturing ofmicromechanical structures within layers of semiconductor material,which have been deposited (for example, a polycrystalline-silicon layer)or grown (for example, an epitaxial layer) on sacrificial layers, whichare removed via chemical etching.

Inertial sensors, for instance, accelerometers and gyroscopes, made withthis technology are used successfully, for example, in the automotivefield, in inertial navigation, or in the field of portable devices.

In particular, integrated gyroscopes of semiconductor material made withMEMS technology are known, which are referred to hereinafter as MEMSgyroscopes.

These MEMS gyroscopes operate on the basis of the principle of relativeaccelerations, exploiting Coriolis acceleration. When an angularvelocity is applied to a mobile mass that is driven in a lineardirection, the mobile mass is subject to an apparent force, or Coriolisforce, which determines a displacement thereof in a directionperpendicular to the linear driving direction and to the axis aboutwhich the angular velocity is applied.

The mobile mass is supported above a substrate via elastic elements thatenable driving thereof in the driving direction and displacement in thedirection of the apparent force, which is directly proportional to theangular velocity.

The displacement of the mobile mass may, for example, be detected via acapacitive transduction system, determining the variations ofcapacitance between mobile electrodes, which are fixed with respect tothe mobile mass, and fixed electrodes, which are fixed with respect tothe substrate.

There is a need for improved structures for inertial sensors, such asMEMS gyroscopes, and for improved methods of forming such structures.

BRIEF SUMMARY

Embodiments of the present disclosure provide detection structures ofMEMS sensor devices, in particular of a MEMS gyroscope, having improvedmechanical and electrical characteristics.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present solution, preferredembodiments thereof are now described, purely by way of non-limitingexample, with reference to the attached drawings, wherein:

FIG. 1 is a schematic top plan view of a micromechanical detectionstructure of a MEMS sensor device, of a known type;

FIG. 2 shows the detection structure of FIG. 1, whose driving movementshave been highlighted;

FIG. 3 is a schematic top plan view of a micromechanical detectionstructure of a MEMS sensor device according to a first embodiment of thepresent disclosure;

FIG. 4 shows the detection structure of FIG. 3, whose driving movementshave been highlighted;

FIG. 5 is a schematic top plan view of a micromechanical detectionstructure of a MEMS sensor device according to a second embodiment ofthe present disclosure;

FIG. 6 shows the detection structure of FIG. 5, whose driving movementshave been highlighted;

FIG. 7 is an overall block diagram of a MEMS sensor device including themicromechanical detection structure of FIG. 3 or 5 according to anotherembodiment of the present disclosure;

FIGS. 8A-8C are top plan views of additional embodiments of the couplingunits of FIG. 5;

FIGS. 9A and 9 b are top views of the driven masses of FIG. 5 showingthe positioning of electrodes beneath of each of the driven masses;

FIGS. 10A and 10B are simplified cross-sectional views illustratingvariable capacitors formed by the first and second driven masses and theelectrodes of FIGS. 9A and 9B; and

FIG. 11 is a schematic top plan view of the micromechanical detectionstructure of the MEMS sensor device of FIG. 5 showing the positioning ofelectrodes beneath the first and second driven masses according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 is a schematic representation of a micromechanical detectionstructure of a MEMS gyroscope, which is designated by 1 and is made in adie of semiconductor material, for example silicon, including asubstrate 2.

The detection structure 1 has a substantially planar configuration witha main dimension or extension in a horizontal plane xy, defined by afirst horizontal axis x and a second horizontal axis y, orthogonal toone another, and substantially parallel to the plane of the substrate 2,and a minor size, dimension, or extension with respect to the aforesaidmain extension, in a direction parallel to a vertical axis z, whichforms, with the first and second horizontal axes x, y, a set of threeorthogonal axes.

The detection structure 1 comprises a first driving mass 4 a and asecond driving mass 4 b, which have dimensions in or extend in thehorizontal plane xy (purely by way of example, substantiallyrectangular), and are connected to respective anchorages 5 a, 5 b, fixedwith respect to the substrate 2, by elastic anchorage elements 6 a, 6 b.The driving masses 4 a, 4 b are suspended over the substrate 2, parallelto the same substrate 2 in a resting condition.

A respective set of driving electrodes 7 a, 7 b is associated with eachdriving mass 4 a, 4 b. Each set of driving electrodes 7 a, 7 b comprisesa respective plurality of mobile electrodes 8 a, 8 b, which are fixedwith respect to the respective driving mass 4 a, 4 b and extendexternally to the driving mass 4 a, 4 b; and a respective plurality offixed electrodes 9 a, 9 b, which are fixed with respect to the substrate2 and are comb-fingered with the mobile electrodes 8 a, 8 b.

Suitable electrical biasing signals from an electronic circuit (notillustrated herein) for driving the MEMS gyroscope, determine, by mutualand alternating electrostatic attraction of the electrodes, anoscillatory driving movement of the driving masses 4 a, 4 b in a lineardriving direction, in the example along the second horizontal axis y. Inparticular, the first and second driving masses 4 a, 4 b are driven inopposite senses of the driving direction, as indicated by the arrows inFIG. 2 described hereinafter.

The elastic anchorage elements 6 a, 6 b are thus configured to becompliant with respect to this driving movement.

The detection structure 1 further comprises a driven mass 10, arrangedbetween the first and second driving masses 4 a, 4 b (in the directionof the first horizontal axis x), and connected to the driving masses 4a, 4 b by elastic connection elements 11 a, 11 b. Also the driven mass10 is suspended above the substrate 2, parallel thereto in the restingcondition.

The driven mass 10 has a main dimension or extension in the horizontalplane xy, for example with a rectangular shape, and centrally defines anempty space 12, the center O of which coincides with the centroid andthe center of symmetry of the entire structure.

A coupling unit 14 is arranged within the empty space 12, configured forelastic coupling and anchoring of the driven mass 10 to the substrate 2.

In particular, the coupling unit 14 comprises a rigid element 15, in theexample having a rectilinear dimension or extension along the firsthorizontal axis x, arranged at the center of the empty space 12,elastically connected to the driven mass 10 by elastic elements (notshown), and further connected, by respective elastic connection elements16 which have, in the example, a linear dimension or extension along thesecond horizontal axis y to central anchorage elements 17.

In use, and as shown schematically in FIG. 2 (where the detectionstructure 1 is shown once again schematically for clarity ofillustration), the coupling unit 14 is configured to enable rotation ofthe driven mass 10 in the plane of the sensor xy (with respect to thesubstrate 2) about the vertical axis z, in response to the drivingmovement in opposite directions of the driving masses 4 a, 4 b (asrepresented by the arrows). Basically, the driven mass 10 is drawn inrotation, in the example in the counterclockwise direction, by themovement of the driving masses 4 a, 4 b.

In response to the driving movement and in the presence of an angularvelocity acting about the first horizontal axis x, a Coriolis force isgenerated on the driving masses 4 a, 4 b directed along the verticalaxis z, which causes a respective rotation of the same driving masses 4a, 4 b out of the plane of the sensor xy, in the example about thesecond horizontal axis y. Suitable electrodes arranged on the substrate2, underneath the driving masses 4 a, 4 b (here not illustrated) enable,by capacitive coupling with the same driving masses 4 a, 4 b, detectionof a quantity indicative of the value of the angular velocity about thefirst horizontal axis x (which thus constitutes a first detection axisfor the MEMS gyroscope).

In a substantially similar way, in response once again to the drivingmovement and in the presence of an angular velocity acting about thesecond horizontal axis y, a Coriolis force is generated on the drivenmass 10 directed along the vertical axis z, which causes a respectiverotation thereof out of the plane of the sensor xy, in the example aboutthe first horizontal axis x. Once again, suitable electrodes arranged onthe substrate 2, underneath the driven mass 10 (here not illustrated)enable, by capacitive coupling with the same driven mass 10, detectionof a quantity indicative of the value of the angular velocity actingabout the second horizontal axis y (which thus constitutes a seconddetection axis for the MEMS gyroscope).

While the detection structure 1 is advantageous from numerous points ofview, the structure may result in undesirable cross-talk betweendetection structures during electrical testing thereof (when they arecoupled to a same testing structure). There may also be vibrationsinduced in a corresponding package due to the driving movement andoscillations and instability of the zero level of the MEMS sensor device(the so-called ZRL—Zero-Rate Level). Moreover, the detection structure 1may have a non-zero sensitivity to undesirable external stresses andvibrations that lead to rotational accelerations about the vertical axisz.

As will be clarified hereinafter, the present solution stems from therealization, by the present Applicant, that the problems highlightedpreviously are in general due to a non-zero resultant of the forces andof the torques exerted by inertial effect on the substrate (and thus onthe corresponding package) by the moving masses (driving masses anddriven masses) at the corresponding anchorages, as a result of thedriving movement.

In particular, referring to FIG. 2, in the detection structure 1 of aknown type a torque is generated on the substrate 2 at the coupling unit14, due to rotation of the driven mass 10 about the vertical axis z.

The present Applicant has realized that the aforesaid torque,transmitted to the substrate 2 and to the package, causes, for example,undesirable couplings with other detection structures duringelectrical-testing operations, or in general undesirable disturbanceeffects.

A particular aspect of the present solution thus envisages, as will bedescribed in detail, first with reference to FIG. 3, providing adetection structure, designated by 20, in which the arrangement andconfiguration of the driving/driven masses and of the correspondingelastic elements for coupling and anchorage to the substrate 2, as wellas the direction of the corresponding driving movements, are such as tooriginate a substantially and ideally zero resultant of the forces andof the torques exerted on the substrate 2 at the correspondinganchorages.

In other words, the inertial effects of the various mobile masses on thesubstrate 2, in terms of forces and torques, are such as to compensateone another.

In detail, in a first embodiment, the detection structure 20 issubstantially equivalent to the detection structure 1 of FIG. 1(elements that are similar are thus not described again herein and aredesignated by the same reference numbers), with the difference that itincludes a first coupling element 22 a and a second coupling element 22b, which elastically couple the driven mass 10 to the first driving mass4 a and to the second driving mass 4 b, respectively.

These coupling elements 22 a, 22 b are configured to generate on thesubstrate 2 a torque such as to substantially compensate the torque dueto rotation of the driven mass 10. The resultant of the torques is thussubstantially zero as a result of the driving movement. These couplingelements 22 a, 22 b cause in particular reversal of the velocity ordriving direction of the driven mass 10, with respect to the traditionalsolution, described with reference to FIG. 2.

Each coupling element 22 a, 22 b is configured to define a rigidconnection element 24 having a first end connected to the driven mass 10and a second end connected to the respective driving mass 4 a, 4 b, soas to define a respective hinged coupling (via respective elastic hingeelements, not illustrated herein).

The rigid connection element 24 has a longitudinal dimension orextension, in the example along the first horizontal axis x, at rest.The aforesaid rigid connection element 24, which may ideally beconsidered as having infinite stiffness to bending, has, in anintermediate portion thereof between the driven mass 10 and therespective driving mass 4 a, 4 b, for example at a central portionthereof, a point of constraint to the substrate 2 (which is forced, thatis, to remain substantially immobile to translation during movement ofthe driving masses 4 a, 4 b). In particular, the aforesaid intermediateportion is hinged to the substrate 2 of the detection structure 20 atthe aforesaid point of constraint, in the example by a pair ofrespective anchorages 25 to which the aforesaid intermediate portion isconnected via respective elastic hinge elements 26.

The rigid connection element 24 is thus ideally hinged at the center tothe substrate 2, and, at its ends, to the driven mass 10 and to therespective driving mass 4 a, 4 b, consequently operating substantiallyas a rocker arm (or as a lever with a central fulcrum).

During operation, as shown schematically in FIG. 4, the rigid connectionelement 24 is free to rotate in the horizontal plane xy about thecentral point of constraint, but not to translate. Consequently, thedriving movement of the driving masses 4 a, 4 b in opposite senses ofthe driving direction (in the example, along the second horizontal axisy) leads in this case to a rotation in a clockwise direction of thedriven mass 10 (i.e., in a direction opposite to that of the knownsolution of FIG. 1).

In particular, as highlighted in the aforesaid FIG. 4, the couplingelements 22 a, 22 b are configured to exert on the substrate 2, at therespective central constraint, a total torque (in a counterclockwisedirection, in the example) equal and opposite to the torque (in aclockwise direction, in the example) exerted on the same substrate 2 bythe coupling unit 14 of the driven mass 10 at the central anchorageelements 17, due to rotation of the same driven mass 10 about thevertical axis z.

Furthermore, in this embodiment, the resultant of the forces exerted onthe anchorages 5 a, 5 b on account of the driving movement of thedriving masses 4 a, 4 b is substantially zero, in so far as the forcesexerted by the individual driving masses 4 a, 4 b are substantiallycompensated (given that the respective driving movements are opposite toone another in the driving direction).

Thus, advantageously, both the resultant of the forces and the resultantof the torques that act on the substrate 2 are substantially zero.

In a way that will be evident from what has been discussed, themechanical characteristics (for example, in terms of the inertial massesand of the stiffnesses of the elastic elements) of the driven mass 10,of the driving masses 4 a, 4 b, and of the respective elements forcoupling and anchorage to the substrate 2 are designed so as to ensuresubstantial equivalence, and thus mutual compensation, of the forces andtorques generated in opposite directions, and substantial cancelling-outof the resultant of forces and torques acting on the substrate 2.

In a possible embodiment, each of the elastic hinge elements previouslydefined may comprise a respective pair of springs, which have alongitudinal dimension or extension (for example, along the secondhorizontal axis y) and are set as prolongation of one another startingfrom the respective hinge point.

With reference to FIG. 5, a description of a second embodiment of thepresent solution is now presented, envisaging a different arrangement ofthe driving/driven masses and of the corresponding elastic elements forcoupling and anchorage to the substrate 2, such as to originate onceagain a substantially zero resultant of the forces and torques exertedon the same substrate 2 at the corresponding anchorages.

In particular, in this second embodiment, the detection structure, onceagain designated by 20, comprises a third driving mass 4 c, in theexample substantially rectangular, having dimensions or extending in thehorizontal plane xy, and connected to respective anchorages 5 c, fixedwith respect to the substrate 2, by respective elastic anchorageelements 6 c. The third driving mass 4 c is suspended above thesubstrate 2, parallel to the same substrate 2 in the resting condition.

The third driving mass 4 c is arranged between the first and seconddriving masses 4 a, 4 b along the first horizontal axis x. A geometricalcenter O of the third driving mass 4 c in this case represents thecentroid and center of symmetry of the detection structure 20.

A respective set of driving electrodes 7 c is associated with the thirddriving mass 4 c, comprising a respective plurality of mobile electrodes8 c, fixed with respect to the same third driving mass 4 c, as well as arespective plurality of fixed electrodes 9 c fixed with respect to thesubstrate 2 and comb-fingered with the mobile electrodes 8 c.

Appropriate electrical biasing signals from the electronic circuit (notillustrated) for driving the MEMS gyroscope, determine, by mutual andalternating electrostatic attraction of the electrodes, a respectivedriving movement of the third driving mass 4 c in a linear drivingdirection, in the example along the second horizontal axis y.

In particular, in this embodiment, as represented by the arrows in thenext FIG. 6, the first and second driving masses 4 a, 4 b are driven inthe same sense of the driving direction, whereas the third driving mass4 c is driven in the opposite sense of the same driving direction.

The detection structure 20 in this case comprises a pair of drivenmasses (suspended above the substrate 2, parallel thereto in the restingcondition), and in particular a first driven mass, designated once againby 10, arranged between the first and third driving masses 4 a, 4 c (inthe direction of the first horizontal axis x), and connected to the samedriving masses 4 a, 4 c by elastic connection elements 11 a, 11 b (forexample, of a linear type); and a second driven mass 30, arrangedbetween the second and third driving masses 4 b, 4 c (in the directionof the first horizontal axis x), and connected to the same drivingmasses 4 b, 4 c by respective elastic connection elements 31 a, 31 b(which are also, for example, of a linear type).

Each driven mass 10, 30 has a main dimension or extension in thehorizontal plane xy, with a shape that is for example rectangular, anddefines at the center an empty space 12, 32, arranged inside which is arespective coupling unit 14, 34 configured for elastic coupling andanchorage of the respective driven mass 10, 30 to the substrate 2.

Each coupling unit 14, 34 comprises a rigid element 15, 35 arranged atthe center of the empty space 12, 32, elastically connected to therespective driven mass 10, 30, and further elastically connected tocentral anchorage elements 17, 37 by respective elastic connectionelements 16, 36, which have, in the illustrated example, a lineardimension or extension, as will now be described in more detail.

In particular, in the example illustrated in FIG. 5, the elasticconnection elements 16 associated with the first driven mass 10 have alinear dimension or extension along the second horizontal axis y,whereas the elastic connection elements 36 associated with the seconddriven mass 30 have a linear dimension or extension along the firsthorizontal axis x (given that they are further configured so as toenable rotations of the same driven masses 10, 30 upon detection ofrespective angular velocities). Furthermore, in the same example of FIG.5, the rigid element 15 coupled to the first driven mass 10 has a lineardimension or extension along the first horizontal axis x, whereas therigid element 35 coupled to the second driven mass 30 has a lineardimension or extension along the second horizontal axis y.

During operation, as shown in FIG. 6, in response to the drivingmovement, the first and second driven masses 10, 30 perform rotations inopposite directions (in the example, the first driven mass 10 in thecounterclockwise direction and the second driven mass 30 in theclockwise direction) in the plane of the sensor xy, with respect to thesubstrate 2 and about the vertical axis z.

Consequently, on the substrate 2 a substantially zero resultant torqueis generated due to rotation of the driven masses 10, 30, in so far asat the respective coupling units 14, 34 and the respective centralanchorage elements 17, 37 torques are generated having substantially thesame value but oriented in opposite directions, thus compensating oneanother.

Once again, in fact, the mechanical characteristics (for example, interms of inertial masses and stiffnesses) of the driven masses 10, 30and of the respective coupling units 14, 34 are designed to obtain theaforesaid substantial equivalence of the torques generated in oppositedirections, and substantial cancelling-out of the resultant torque onthe substrate 2.

Also in this case, the resultant of the forces exerted on the anchorages5 a, 5 b, 5 c on account of the driving movement of the driving masses 4a, 4 b, 4 c is substantially zero, in so far as the forces exerted bythe individual driving masses 4 a, 4 b, 4 c (in a first sense of thedriving direction for the first and second driving masses 4 a, 4 b, andin a second sense of the same driving direction for the third drivingmass 4 c) are substantially compensated, once again thanks to theappropriate sizing of the mechanical characteristics of the drivingmasses 4 a, 4 b and 4 c and of the corresponding coupling and anchorageelastic elements.

In this case, the detection movements are performed by the first andsecond driven masses 10, 30, which are able to turn, as a result of theCoriolis forces that are generated due to the driving movement, forexample about the first horizontal axis x and the second horizontal axisy, respectively.

The advantages of the solution proposed are clear from the foregoingdescription.

In any case, it is emphasized once again that the present solutionenables provision of micromechanical detection structures, in particularfor MEMS sensor devices, for example MEMS gyroscopes, with asubstantially zero resultant of the forces and of the torques acting onthe substrate at the anchorages of the moving masses.

In this way, it is possible to prevent transmission of undesirablestresses from the micromechanical detection structure to the substrateand the package of the sensor device, thus solving the problemshighlighted previously, amongst which: undesirable couplings betweendetection structures during electrical testing thereof; vibrationsinduced in the corresponding package following upon the drivingmovement; oscillations and instability of the zero level; andsensitivity to undesirable external stresses and vibrations that lead torotational accelerations about the vertical axis z.

Even though both of the embodiments described previously have the sameadvantageous characteristics highlighted above, the first embodiment(FIG. 3) may, however, be more advantageous than the second embodiment(FIG. 5), at least in some circumstances, for example owing to thepresence of a smaller number of moving masses, a better area occupation,a smaller number of elastic coupling elements, and a greater resultingsimplicity of construction and greater insensitivity to manufacturingprocess spread.

In any case, as mentioned previously, it is advantageous to use thedetection structure 20 in a MEMS sensor device.

In this regard, FIG. 7 shows schematically a sensor device 40, forexample a MEMS gyroscope, comprising the detection structure 20,designed to generate at least one electrical detection quantity as afunction at least one quantity of interest (for example, an angularvelocity, in the case of a gyroscope); and an electronic circuit 42 (aso-called ASIC—Application-Specific Integrated Circuit), electricallycoupled to the detection structure 20 and designed to supply driving andbiasing electrical quantities to the detection structure 20 and furtherdesigned to process the electrical quantities detected, for example byamplification and filtering operations.

In particular, the detection structure 20 and the electronic circuit 42may be made in respective dies of semiconductor material, which arehoused in a same package 44, for example in a configuration where theyare arranged side-by-side or vertically stacked on top of one another.

FIGS. 8A-8C are top plan views of additional embodiments of the couplingunits 14 and 34 of FIG. 5, each of which provides net zero forces andtorques applied to the substrate 2 on which the detection structure 20is formed. In FIG. 8A, a coupling unit 34 a may be used in associationwith the first driven mass 10 or the second driven mass 30 in variousembodiments of the detection structure 20. Whether utilized inassociation with the first or second driven masses 10 and 30, thecoupling structure 34 a is positioned within the aperture or empty space32 in the center of each of the first and second driven masses. Thisempty space 32 is designated 32 a in the embodiment of FIG. 8A. Thecoupling unit 34 a includes two anchorage elements 37 a that are spacedapart along the Y-axis direction and are attached to or formed as partof the substrate 2 on which the detection structure 20 including thecoupling unit is formed. The driven mass 10, 30 (not shown) iselastically connected to the anchorage elements 37 a, and thereby to thesubstrate 2, through a rigid connection structure 35 a and an elasticconnection structure 36 a.

In the embodiment of FIG. 8A, the rigid connection structure 35 a isconnected to the driven mass 10, 30 through tab portions 35 a-1extending along the Y-axis and further includes an inner square portion35 a-2 connected to the tab portions. The inner square portion 35 a-2surrounds, in the XY plane, the anchorage elements 37 a and the elasticconnection structure 36 a. The elastic connection structure 36 aincludes a first elastic portion 36 a-1 extending along the X-axisdirection and connected at each end to the inner square portion 35 a-2.A second elastic portion 36 a-2 extends along the Y-axis direction andconnects each of the anchorage elements 37 a to the first elasticportion 36 a-1. In operation, the elastic connection structure 36 aenables driving of the associated driven mass 10, 30 (not shown in FIG.8A) in the driving direction and displacement of the driven mass in thedirection of the apparent force, which is directly proportional to theangular velocity, as will be appreciated by those skilled in the art.

In the embodiment of FIG. 8B, a coupling unit 34 b may be used inassociation with the first driven mass 10 or the second driven mass 30in various embodiments of the detection structure 20. Once again,whether utilized in association with the first or second driven masses10 and 30, the coupling structure 34 b is positioned within the apertureor empty space 32 b in the center of each of the first and second drivenmasses. The coupling unit 34 b includes four anchorage elements 37 bthat are spaced apart along the X- and Y-axes and are attached to orformed as part of the substrate 2 on which the detection structure 20including the coupling unit is formed. The driven mass 10, 30 (notshown) is elastically connected to the anchorage elements 37 b, andthereby to the substrate 2, through a rigid connection structure 35 band an elastic connection structure 36 b.

In the embodiment of FIG. 8B, the rigid connection structure 35 bextends along the Y-axis direction and is connected at each end to thedriven mass 10, 30, with two anchorage elements 37 a being positioned tothe left and two to the right of the rigid connection structure. Theelastic connection structure 36 b includes two first elastic portions 36b-1, one to the left of the rigid connection structure 36 b and one tothe right. Each first elastic portion 36 b-1 extends along the Y-axisdirection and is connected at each end to one of the adjacent anchorageelements 37 b. The elastic connection structure 36 b further includestwo second elastic portions 36 b-2, one to the left and one to the rightof the rigid connection structure 35 b. Each second elastic portion 36b-2 extends along the X-axis direction and connects at one end to one ofthe first elastic portions 36 b-1 and at the other end to the rigidconnection structure 35 b. In operation, the elastic connectionstructure 36 b enables driving of the associated driven mass 10, 30 (notshown in FIG. 8B) in the driving direction and displacement of thedriven mass in the direction of the apparent force, which is directlyproportional to the angular velocity.

The embodiment of FIG. 8C includes a coupling unit 34 c that may be usedin association with the first driven mass 10 or the second driven mass30 in various embodiments of the detection structure 20. Once again,whether utilized in association with the first or second driven masses10 and 30, the coupling structure 34 c is positioned within the apertureor empty space 32 c in the center of each of the first and second drivenmasses. The coupling unit 34 c includes four anchorage elements 37 cthat are spaced apart along the X- and Y-axes and are attached to orformed as part of the substrate 2 on which the detection structure 20including the coupling unit is formed. The driven mass 10, 30 (notshown) is elastically connected to the anchorage elements 37 b, andthereby to the substrate 2, through a rigid connection structure 35 cand an elastic connection structure 36 c.

In the embodiment of FIG. 8C, the rigid connection structure 35 cincludes first and second rigid elements 35 c-1 and 35 c-2, eachextending along the Y-axis direction and being spaced apart in theX-axis direction. Each of the first and second rigid elements 35 c-1 and35 c-2 is connected at upper and lower ends to the driven mass 10, 30.The first and second rigid elements 35 c-1, 35 c-2 are positioned in thecenter of the empty space 32 c, with two anchorage elements 37 c beingpositioned to the left and two to the right of the first and secondrigid elements. The elastic connection structure 36 c includes two firstelastic portions 36 c-1, one to the left of the rigid connectionstructure 36 c and one to the right. Each first elastic portion 36 c-1extends along the Y-axis direction and is connected at each end to oneof the adjacent anchorage elements 37 b. The elastic connectionstructure 36 c further includes two second elastic portions 36 c-2, oneto the left and one to the right of the rigid connection structure 35 c.Each second elastic portion 36 c-2 extends along the X-axis directionand connects at one end to one of the first elastic portions 36 c-1 andat the other end to one of the first and second rigid elements 35 c-1and 35 c-2. Once again, in operation the elastic connection structure 36c enables driving of the associated driven mass 10, 30 (not shown inFIG. 8C) in the driving direction and displacement of the driven mass inthe direction of the apparent force.

FIGS. 9A and 9 b are top views of the driven masses 30 and 10,respectively, of FIG. 5 showing the positioning of electrodes E1, E2beneath of each of the driven masses, as will now be described in moredetail. The positioning of the electrodes E1, E2 for each axis dependson the orientation of the flexible or elastic structure associated withthe driven mass 30, 10. In the embodiment of FIG. 9A, the coupling unit34 formed by the rigid element 35, elastic connection elements 36 andanchorage elements 37 are arranged so that a roll (R) axis correspondsto the X-axis and the structure allows the detection of an angularvelocity or rate acting on the Y-axis. In FIG. 9B, the coupling unit 14formed by the rigid element 15, elastic connection elements 16 andanchorage elements 37 are arranged so that a pitch (P) axis correspondsto the Y-axis and the structure allows the detection of an angularvelocity or rate acting on the X-axis. In the embodiments of FIGS. 9Aand 9B, the electrodes E1, E2 are contained within the footprint orcompletely underneath each driven mass 10, 30, and are symmetric withrespect to the center of rotation C of each driven mass.

FIGS. 10A and 10B are simplified cross-sectional views illustratingvariable capacitors C1, C2 formed by the driven masses 10, 30 and theelectrodes E1, E2 of FIGS. 9A and 9B. Rotation about the roll axis R orX-axis in FIG. 10A results in changes in the values of the variablecapacitors C1, C2, with one capacitor value increasing and the otherdecreasing, depending on the direction of rotation. The values of thecapacitors C1, C2 indicate or allow for the detection of the angularvelocity or rate acting on the Y-axis. Similarly, rotation about thepitch axis P or Y-axis in FIG. 10B results in changes in the values ofthe variable capacitors C1, C2, with one capacitor value increasing andthe other decreasing, once again depending on the direction of rotation.The values of the capacitors C1, C2 indicate or allow for the detectionof the angular velocity or rate acting on the X-axis.

FIG. 11 is a schematic top plan view of the micromechanical detectionstructure 20 of the MEMS sensor device of FIG. 5 showing the positioningof electrodes E1, E2 beneath each of the first and second driven masses10, 30 according to one embodiment of the present disclosure. Thisfigure illustrates the embodiments of the driven masses 10, 30 of FIGS.9A and 9B contained within the detection structure 20. The electrodesE1, E2 associated with the driven mass 30 are associated with the rollaxis R as discussed with reference to FIG. 9A and are thus indicated asR1 and R2 in FIG. 11. Similarly, the electrodes E1, E2 associated withthe driven mass 10 are associated with the pitch axis P as discussedwith reference to FIG. 9B and thus are indicated as P1 and P2 in FIG.11. The detection structure 20 of FIG. 11 provides in-plane driving ofthe driven masses 10, 30 in that these masses are driven in the XYplane, and provides out-of-plane sensing since variations in thepositions of these driven masses in the Z-direction are sensed.

Finally, it is clear that modifications and variations may be made towhat has been described and illustrated herein, without therebydeparting from the scope of the present solution, as defined in theannexed claims.

In this regard, it is emphasized once again that different embodimentsmay be envisaged, in addition to what has been illustrated previously byway of example, in which, in any case, the configuration and arrangementof the moving masses and of the corresponding elastic elements forcoupling and anchorage to the substrate is such as to lead, followingupon or in response to the appropriate driving movement, to a resultantforce and a resultant twisting moment on the substrate that aresubstantially zero.

In particular, different kinematic arrangements of the moving masses,and different configurations of the corresponding elements for anchorageto the substrate, may be envisaged.

Furthermore, it is emphasized that the solution described may findadvantageous application in bi-axial or tri-axial micromechanicaldetection structures, in MEMS gyroscopes, or also in different andfurther MEMS devices of an inertial type, in which it is desired tocancel out the resultant of the forces and torques acting on thesubstrate, or in any case to reduce them markedly, for example by atleast a factor of ten.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

The invention claimed is:
 1. A device, comprising: a substrate; adriving mass elastically coupled to the substrate, the driving massconfigured to be driven in a driving movement; a first driven masselastically coupled to the driving mass, the first driven mass defininga first opening in a central region thereof; a first coupling assemblyin the first opening of the first driven mass, the first couplingassembly including: a first rigid connection element having a first endconnected to a first edge of the first driven mass in the first opening,and a second end connected to a second edge of the first driven mass inthe first opening, the first and second edges facing one another acrossthe first opening; a plurality of first anchorage elements within thefirst opening and coupled to the substrate; and at least one elasticconnection element elastically connecting the first rigid connectionelement to the plurality of first anchorage elements; a second drivenmass elastically coupled to the driving mass, the driving masspositioned between the first driven mass and the second driven mass, thesecond driven mass defining a second opening in a central regionthereof; and a second coupling assembly in the second opening of thesecond driven mass, the second coupling assembly coupling the seconddriven mass to the substrate.
 2. The device of claim 1 wherein the firstrigid connection element has a first side between the first and secondends and a second side between the first and second ends, the first andsecond sides spaced apart from one another, and the at least one elasticconnection element includes a first portion connected between the firstand second sides of the first rigid connection element, the firstportion extending along a first direction.
 3. The device of claim 2wherein the at least one elastic connection element includes a secondportion extending along a second direction that is transverse to thefirst direction, the second portion connected between first and secondfirst anchorage elements of the plurality of first anchorage elements.4. The device of claim 1 wherein the first rigid connection elementextends along a first direction between the first and second ends, andthe at least one elastic connection element includes: a first elasticconnection element having a first portion extending along the firstdirection between a first pair of the first anchorage elements, and asecond portion extending along a second direction between the firstportion of the first elastic connection element and the first rigidconnection element, the second direction being transverse to the firstdirection; and a second elastic connection element having a firstportion extending along the first direction between a second pair of thefirst anchorage elements, and a second portion extending along thesecond direction between the first portion of the second elasticconnection element and the first rigid connection element.
 5. The deviceof claim 1 wherein the first rigid connection element includes a firstrigid element portion extending along a first direction between thefirst and second ends, and a second rigid element portion extendingalong the first direction between the first and second ends, the firstand second rigid element portions spaced apart from one another along asecond direction that is transverse to the first direction, and the atleast one elastic connection element includes: a first elasticconnection element having a first portion extending along the firstdirection between a first pair of the first anchorage elements, and asecond portion extending along the second direction between the firstportion of the first elastic connection element and the first rigidelement portion; and a second elastic connection element having a firstportion extending along the first direction between a second pair of thefirst anchorage elements, and a second portion extending along thesecond direction between the first portion of the second elasticconnection element and the second rigid element portion.
 6. The deviceof claim 1, further comprising: a first electrode between the substrateand the first driven mass; and a second electrode between the substrateand the first driven mass, the first and second electrodes spaced apartfrom one another along a first direction by the first opening of thefirst driven mass, wherein a first capacitance between the firstelectrode and the first driven mass varies in response to rotation ofthe first driven mass about a first axis extending in a second directionthat is transverse to the first direction, and a second capacitancebetween the second electrode and the first driven mass varies inresponse to the rotation of the first driven mass about the first axis,and the first and second capacitances vary oppositely with respect toone another.
 7. The device of claim 6 wherein the first and secondelectrodes are completely overlapped by the first driven mass.
 8. Thedevice of claim 6 wherein the first and second electrodes are spacedapart from the first axis by a same distance.
 9. The device of claim 6,wherein the second coupling assembly includes: a second rigid connectionelement having a first end connected to a first edge of the seconddriven mass in the opening, and a second end connected to a second edgeof the second driven mass in the opening, the first and second edgesfacing one another across the second opening; a plurality of secondanchorage elements within the second opening; and at least one elasticconnection element elastically connecting the second rigid connectionelement to the plurality of second anchorage elements.
 10. The device ofclaim 9, further comprising: a third electrode between the substrate andthe second driven mass; and a fourth electrode between the substrate andthe second driven mass, the third and fourth electrodes spaced apartfrom one another along the second direction by the second opening of thesecond driven mass, wherein a third capacitance between the thirdelectrode and the second driven mass varies in response to rotation ofthe second driven mass about a second axis extending in the firstdirection, and a fourth capacitance between the fourth electrode and thesecond driven mass varies in response to the rotation of the seconddriven mass about the second axis, and the third and fourth capacitancesvary oppositely with respect to one another.
 11. The device of claim 9wherein the second rigid connection element from the first edge of thesecond driven mass to the second edge of the second driven mass in adirection that is transverse to a direction in which the first rigidconnection elements extends from the first edge of the first driven massto the second edge of the first driven mass.
 12. The device of claim 9wherein the device is a microelectromechanical systems (MEMS) detectionstructure, and the driving mass has a geometrical center located at acentroid and center of symmetry of the MEMS detection structure.
 13. AMEMS sensor device, comprising: a micromechanical detection structure,including: a substrate; a first driving mass elastically coupled to thesubstrate, the first driving mass configured to be driven in a drivingmovement; a first driven mass elastically coupled to the first drivingmass, the first driven mass defining a first opening in a central regionthereof; a first coupling assembly in the first opening of the firstdriven mass, the coupling assembling including: a first rigid connectionelement having a first end connected to a first edge of the first drivenmass in the first opening, and a second end connected to a second edgeof the first driven mass in the first opening, the first and secondedges facing one another across the first opening; a plurality of firstanchorage elements within the first opening; and at least one elasticconnection element elastically connecting the first rigid connectionelement to the plurality of first anchorage elements; a second drivenmass elastically coupled to the driving mass, the driving masspositioned between the first driven mass and the second driven mass, thesecond driven mass defining a second opening in a central regionthereof; a second coupling assembly in the second opening of the seconddriven mass, the second coupling assembly coupling the second drivenmass to the substrate; and an electronic circuit electrically coupled tothe micromechanical detection structure and configured to supplyelectrical driving and biasing signals to the micromechanical detectionstructure and to process at least one electrical signal output by themicromechanical detection structure.
 14. The MEMS sensor device of claim13 wherein the micromechanical detection structure and the electroniccircuit are integrated in respective semiconductor dies housed in a samepackage.
 15. The MEMS sensor device of claim 13 wherein themicromechanical detection structure and the electronic circuit areconfigured to form a biaxial or triaxial MEMS gyroscope.
 16. The MEMSsensor device of claim 13, wherein the second coupling assemblyincludes: a second rigid connection element having a first end connectedto a first edge of the second driven mass in the opening, and a secondend connected to a second edge of the second driven mass in the opening,the first and second edges facing one another across the second opening;a plurality of second anchorage elements within the second opening; andat least one elastic connection element elastically connecting thesecond rigid connection element to the plurality of second anchorageelements.
 17. The MEMS sensor device of claim 16, further comprising: asecond driving mass elastically coupled to the substrate and to thefirst driven mass, the first driven mass positioned between the firstdriving mass and the second driving mass; and a third driving masselastically coupled to the substrate and to the second driven mass, thesecond driven mass positioned between the first driving mass and thethird driving mass.
 18. A method, comprising: forming a first couplingassembly in a first opening of a first driven mass, the first couplingassembly including a first rigid connection element having a first endconnected to a first edge of the first driven mass in the first opening,and a second end connected to a second edge of the first driven mass inthe first opening, the first and second edges facing one another acrossthe first opening; elastically connecting the first rigid connectionelement to a plurality of first anchorage elements within the firstopening, the first anchorage elements mechanically coupled to asubstrate; elastically coupling a driving mass the substrate, thedriving mass configured to be driven in a driving movement; forming asecond coupling assembly in a second opening of a second driven mass,the second coupling assembly including a second rigid connection elementhaving a first end connected to a first edge of the second driven massin the second opening, and a second end connected to a second edge ofthe second driven mass in the second opening, the first and second edgesfacing one another across the second opening; elastically connecting thesecond rigid connection element to a plurality of second anchorageelements within the second opening, the second anchorage elementsmechanically coupled to the substrate; and elastically coupling thesecond driven mass to the driving mass, the driving mass positionedbetween the first driven mass and the second driven mass.
 19. The methodof claim 18, further comprising: elastically coupling a second drivingmass to the substrate and to the first driven mass, the first drivenmass positioned between the first driving mass and the second drivingmass; and elastically coupling a third driving mass to the substrate andto the second driven mass, the second driven mass positioned between thefirst driving mass and the third driving mass.
 20. The method of claim18, further comprising: forming a first electrode between the substrateand the first driven mass; forming a second electrode between thesubstrate and the first driven mass, the first and second electrodesspaced apart from one another along a first direction by the firstopening of the first driven mass; forming a third electrode between thesubstrate and the second driven mass; and forming a fourth electrodebetween the substrate and the second driven mass, the third and fourthelectrodes spaced apart from one another along a second direction by thesecond opening of the second driven mass, the second direction beingtransverse to the first direction.